Quick Answer:
A sulfur (rotten egg) odor that comes back on a regular schedule usually means the source isn’t fully fixed. It can be bacteria in the hot water system, a recurring well contamination, or a trap/drain that intermittently dries or allows gas through. Start by identifying whether the smell is in hot or cold water, log how many days pass after you flush or treat a system, and follow a few basic checks before deciding whether to call a pro.
Why This Happens
Common causes of a repeating sulfur smell include:
- Bacterial regrowth: Certain bacteria produce hydrogen sulfide gas when they use sulfur compounds in water. If the bacteria aren’t fully removed, the smell can return in cycles.
- Water heater issues: A reacting anode rod or warm conditions in the tank create ideal conditions for hydrogen sulfide; smell that appears only in hot water points to the heater.
- Well or source water changes: Seasonal changes, aquifer movement, or temporary contamination can make sulfur levels rise and fall.
- Dry or broken traps and venting problems: Intermittent gas entry from drains or sewers will cause a recurring odor in parts of the house.
Step-by-Step What to Do
1. Confirm where the smell is coming from
- Check both hot and cold taps, showers, and outside faucets. Smell a glass of cold water and a glass of hot water separately.
- If the smell appears only with hot water, focus on the water heater. If it’s in cold water or all taps, the source may be the supply or well.
- If you need more focused reading about hot-water specific issues, note the link text Rotten egg smell in hot water for later reference.
2. Do simple plumbing checks
- Run each fixture for a minute to flush standing water and then re-check for smell.
- Make sure all floor drains and fixture traps contain water and aren’t allowing sewer gas through.
- Vent pipes should be clear of debris or nests; a blocked vent can cause odd odors.
3. Flush and keep a log
- Flush the water heater and run several minutes of hot water at each tap to move fresh water through the system.
- After any flushing or treatment, log the date and time and note the number of days until the odor returns. Keep a simple notebook or phone note with entries like “Flush 1/10 — odor returned 1/18 (8 days).” This helps spot a pattern.
4. Try targeted fixes if appropriate
- Replace a sacrificial anode rod in older water heaters if it’s reacting and producing odor.
- Disinfect a private well with a properly applied shock chlorination if you suspect well contamination; record the date and monitor the log for recurrence.
- If the odor came on suddenly from a private supply, consider the note Rotten smell in well water suddenly as a reminder to investigate source changes.
5. Monitor and re-evaluate
- Watch the log for how many days the treatment buys you. Short intervals (days to a few weeks) suggest the underlying source remains active and needs professional assessment.
- If a simple flush stops the smell for months, a one-time cleaning may have been enough.
What Not to Do
- Do not ignore cyclical sulfur smell patterns. Repeating smells indicate an ongoing issue that can worsen or signal contamination.
- Do not pour random chemicals down drains or into the water heater without guidance — this can damage plumbing or create hazardous mixes.
- Do not assume the smell is only a nuisance; avoid prolonged exposure to strong, concentrated gas if it makes you feel unwell.
When to Call a Professional
- Persistent smell that returns within days or weeks despite flushing and basic fixes.
- Smell that is only in hot water after replacing the anode or flushing the heater — a plumber or water treatment specialist can inspect the tank and hookup a proper treatment.
- Well owners who suspect contamination: contact a licensed well contractor or your local health department for testing and remediation.
- If household members experience headaches, dizziness, nausea, or other symptoms when the smell is present, seek help promptly.
Safety Notes
- Hydrogen sulfide smells like rotten eggs at low levels. At high levels it can be hazardous. If you smell a very strong rotten-egg odor and feel ill, leave the area and call emergency services.
- Do not use open flames (matches, pilot lights) if you detect a persistent, strong gas-like odor in the home.
- Wear gloves and eye protection when handling water-treatment chemicals and follow label directions exactly. If unsure, hire a professional.
Common Homeowner Questions
- Q: Is the smell dangerous? A: Small amounts are usually only a nuisance, but strong concentrations or symptoms require immediate action.
- Q: Will a one-time flush stop it? A: It can temporarily remove the smell, but logging how many days until it returns tells you if the problem is permanent.
- Q: Can I fix this myself? A: Basic checks and flushing are DIY, but recurring or source-water problems are best handled by professionals.
For more related articles, see the Sulfur / Rotten Egg Smell in Water hub.